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<div class="moz-cite-prefix">(From memory & without firing up a
compiler to verify) ...<br>
<br>
Sets are implemented as bitmaps with one bit allocated to each
possible value of the set type (hence the limitations on the
number of possible elements in the set).<br>
<br>
So if you have<br>
type bytesset = [0..7]; // 8 possible values<br>
var a: bytesset ;<br>
begin<br>
if a in [1,4] then<br>
<br>
The set literal [1,4] ends up as a byte with the value $0A.<br>
The test "a in [1,4]" is equivalent to "(a AND $0A) <> 0".<br>
<br>
The generated code (for a set of this size) is an AND followed by
a conditional jump. Very efficient.<br>
<br>
It gets a little nastier when the possible values gets larger as
the size of the set grows (set of AnsiChar is 32 bytes; Set of
Widechar exceeds the permissible size of a set).<br>
<br>
The precise code generated by case varies between jump tables and
linear comparisons.<br>
<br>
Regards<br>
<br>
<br>
On 8/06/2016 5:27 p.m., Steve Peacocke wrote:<br>
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<div>If I remember correctly, the compiler changes both to array
anyway so you come out with exactly the same compiled code. </div>
<div id="AppleMailSignature"><br>
</div>
<div id="AppleMailSignature">Perhaps someone can confirm this or
tell me how wrong I am?<br>
<br>
Steve Peacocke
<div>+64 220 612-611</div>
<div><br>
</div>
</div>
<div><br>
On 8/06/2016, at 4:56 PM, Ross Levis <<a
moz-do-not-send="true" href="mailto:ross@stationplaylist.com"><a class="moz-txt-link-abbreviated" href="mailto:ross@stationplaylist.com">ross@stationplaylist.com</a></a>>
wrote:<br>
<br>
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<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D">I’m wondering
which is more efficient to process...<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D">if (a=1) or (a=2)
then ...<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D">or<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D">if a in [1,2]
then ...<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D">If the answer is
the first method, does it make a difference if more
numbers are checked, eg. if a in [1..3,5] then<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:12.0pt;color:#1F497D">Cheers.</span><span
style="font-size:12.0pt;color:#1F497D"><o:p></o:p></span></p>
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